Measurement and analysis of three-dimensional specular gas tungsten arc weld pool surface

Measurement of weld pool surface is a difficult but urgent task in the welding community. It plays an important role not only in developing the nextgeneration intelligent welding machines but also for modeling complex welding processes. In recent years, different techniques have been applied in this area, but the specular characteristic of weld pool surface and the strong welding arc compromise their effectiveness. To better resolve this problem, a new vision-based sensing (measurement) system was proposed in our previous study, which utilizes the reflection property of the weld pool surface. In that system, a dot-matrix pattern of structured laser light was projected onto the specular weld pool surface and its reflection was imaged on a self-designed imaging plane. Then the distorted reflected image (pattern) was captured and processed. Based on the obtained information, two reconstruction schemes named interpolation reconstruction scheme (IRS) and extrapolation reconstruction scheme (ERS), are proposed in this paper in order to rebuild the three-dimensional weld pool surface off-line. The experimental results verify the effectiveness of the proposed methods and show that ERS can achieve better accuracy than IRS. Meanwhile, the variation of the weld pool surface in an experiment is also analyzed by using the proposed measurement system and extrapolation reconstruction scheme.